Track share funnel actions

[shilman]

@ghengeveld I think this one is pretty uncontroversial.

Summary

Replaces the Share popup's screen-impression telemetry with action-style telemetry so the funnel records the user interactions that drive each transition.

This PR is stacked on #442.

Action	Trigger	Screen
openShare	Share popup opens	Toolbar
publish	User clicks Publish on the welcome screen	ShareWelcome
signIn	User clicks Sign in	ShareSignIn
signInWithSSO	User chooses SSO sign-in	ShareSignIn
submitSubdomain	User submits an SSO subdomain	ShareSubdomain
goBack	User returns from the subdomain screen	ShareSubdomain

All events include entryPoint: toolbar and location: SharePopup. The previous share-welcome-viewed, share-signin-viewed, and share-sso-viewed screen events are removed.

Test plan

• yarn gate
• 29 test files / 221 tests pass

[codecov]

Codecov Report

❌ Patch coverage is 0% with 42 lines in your changes missing coverage. Please review.
⚠️ Please upload report for BASE (shilman/action-telemetry@0f90147). Learn more about missing BASE report.

Files with missing lines	Patch %	Lines
src/screens/SharePopup/SharePopup.tsx	0.00%	29 Missing ⚠️
src/screens/SharePopup/ShareToolbarButton.tsx	0.00%	13 Missing ⚠️

Additional details and impacted files

@@                     Coverage Diff                     @@
##             shilman/action-telemetry     #443   +/-   ##
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  Coverage                            ?   74.18%           
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  Files                               ?      164           
  Lines                               ?    12923           
  Branches                            ?     1142           
===========================================================
  Hits                                ?     9587           
  Misses                              ?     3319           
  Partials                            ?       17           

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[Copilot]

Pull request overview

Updates Share popup telemetry to record funnel actions (open/publish/sign-in/subdomain/back) instead of emitting “screen viewed” impression events, aligning Share’s instrumentation with the action-based funnel approach introduced in #442.

Changes:

• Extends the global TelemetryAction vocabulary with openShare and publish.
• Emits action telemetry for Share popup open + key user interactions (publish, sign-in choices, subdomain submit, back).
• Replaces prior “view” telemetry tests with action-oriented assertions.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

File	Description
src/utils/TelemetryContext.tsx	Adds openShare/publish to the typed action vocabulary.
src/screens/SharePopup/useShareExecution.ts	Emits an openShare action once per Share popup mount.
src/screens/SharePopup/SharePopup.tsx	Emits action telemetry from user interaction handlers across Share funnel screens.
src/screens/SharePopup/SharePopup.test.tsx	Updates tests to validate the new top-of-funnel action telemetry behavior.

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